The present invention relates to electrical devices and more particularly relates to an apparatus for and method of inhibiting an electrical control device connected to a communications network.
A growing trend within the electrical device industry is to enable previously stand alone electrical devices, such as sensors and lighting control devices, to communicate with each other over some type of communications network. Previously, sensor, switch and control devices communicated using point to point connections. Nowadays, manufacturers are building into these devices communication means to enable them to communicate over local area networks (LANs). A variety of systems are currently commercially available which electrical device manufacturers can integrate into their products to enable them to communicate over a network.
One such system is the CEBus system which has been made an EIA standard, the EIA 600 standard, and was originally developed by Intellon Corp. A second system is the LonWorks system commercially available from and developed by Echelon Corp. Both the CEBus and LonWorks systems specify physical and link layer means for communicating over a variety of different media including power line, coaxial cable, fiber optic cable, radio frequency (RF), infrared (IR) and twisted pair cable.
For example, in the area of lighting, it is possible to wire an electrical load to multiple switches such that turning any of the switches on functions to turn the load on. The wiring circuits for two and three way switches are well known and relatively simple to implement. As the number of switches increases, e.g., four way, five way and beyond, the wiring circuits become extremely complicated and unwieldy.
Utilizing one of these systems makes it much easier to design electrical systems which comprise a plurality of different sensing and control devices. Using the lighting example presented above, it is a straight forward application to implement a lighting system whereby multiple sensors or switches control the same lighting control device. For example, each device within a mixture of multiple occupancy sensors, switches or other types of sensor/switch devices can be configured to activate and control the same lighting control device.
However, a disadvantage is when maintenance or service is required to be performed on any of the input sensing or dimming devices controlling or connected to the same lighting control device. Although one of the devices is disabled or placed in an off mode, any of the other devices is still free to activate the application of electrical power to the load.
The present invention is an apparatus for and method of inhibiting and overriding the normal operating mode of one or more input devices connected to a communications network. The present invention is intended to function within an electrical network that is made up of a plurality of input devices wherein a group of input devices is capable of commanding an electrical control device to apply and remove electrical power from an electrical load connected thereto. The input devices or nodes communicate with the electrical control device over a communications network. Such electrical networks can be implemented, for example, utilizing the CEBus (EIA-600 standard) or LonWorks communications systems.
The input devices may comprise any type of sensor such as an occupancy sensor or may comprise a switch or dimming control input. The electrical control device may comprise any switching or dimming control device such as a common circuit breaker or other load breaking/dimming device.
When one of the input devices is turned off, the present invention is operative to inhibit the normal operating mode of all the other input sensors. Note that throughout this document, xe2x80x98turning a device offxe2x80x99 includes switching the device off, disabling the device, placing the device in standby mode or tripping the device. There can be multiple input devices simultaneously in the off, disabled, standby or tripped mode. The electrical control device remains inhibited until all the input devices are no longer in the off, disabled, standby or tripped mode. Thus, electrical power to the load controlled by the electrical control device remains disconnected until all input devices are in the on position.
The present invention is particularly suited to permit maintenance or service to be performed in a safe manner on any of the input devices logically connected to the same electrical control device, i.e., switching or dimming control device. The present invention has been embodied in a series of electrical device products that have been adapted to operate in a LonWorks system. For example, the occupancy sensor catalog no. L778-T and the dimming control unit catalog no. L206-CT, both manufactured by Leviton Manufacturing Co., Inc., Little Neck, N.Y. implement the method of the present invention.
Each input device comprises switch means for placing the input device into an off, disabled, standby, tripped or maintenance inhibit mode. The switch means can be implemented using mechanical or electronic means or a combination of the two either at the device itself or remotely over a network via one or more control commands. A pull out tab or mechanical arm can be used to put the input device into the maintenance off mode when it is pulled out. The pull out tab or mechanical arm would leave the input device in normal operating mode when pushed back in.
In either case, when the input device is placed in the off position, an inhibit message is sent to the electrical control device. In response, electrical power to the attached load is removed. Subsequently, all other input devices are inhibited from applying power to said load. This permits safe access to the electrical control device or to the load for service or maintenance reasons. The normal operating mode of all the input devices connected to the same electrical control device is inhibited or overridden. Until all input devices that have previously been placed in the off mode are put into the on mode and returned to their normal operating condition, all input devices are not permitted to change the state of the load or the electrical control device.
Local and remote signaling, control and indication (on a network management tool, for example) is also provided when any device is being tested, fails or passes the tests, fails, requires testing or is in a degraded state and is about to fail. This includes remote diagnostic monitoring and control by a remote entity such as a network management tool connected to the network. Nodes report their status either automatically at periodic intervals or in response to queries by a management entity.
There is thus disclosed in accordance with the present invention a method of inhibiting the normal operating mode of a plurality of nodes logically connected to an electrical control device, the method comprising the steps of placing at least one of the nodes into the off state, communicating to the electrical control device the fact that the node has been placed on the off sate and inhibiting the electrical control device; in response to the communication, from activating an electrical load connected thereto until each of the plurality of nodes is removed from the off state.
In addition, the plurality of nodes and the electrical control device are adapted to communicate over a communications network. The plurality of nodes and the electrical control device may be adapted to operate in a LonWorks compatible system or a CEBus compatible system. The method also comprises the step of providing switch means at each node permitting a user to place the node in the off state. The method also comprises the step of inhibiting each node from instructing the electrical control device to apply electrical power to the electrical load.
The method also comprises the steps of maintaining a table of node identifiers, adding an identifier associated with a node to the table when a node has been placed in the off state, removing the identifier associated with a node from the table when the node has been removed from the off state and enabling the electrical control device to activate an electrical load connected thereto when all node identifiers have been removed from the table, wherein the node identifier may comprise the address of the node.
There is also disclosed in accordance with the present invention, in an electrical network including a plurality of input devices and an electrical control device coupled to and controlling electrical power to an electrical load, the input devices and the electrical control device adapted to communicate over a communications network, a method of inhibiting the normal operation of the input devices, the method comprising the steps of inhibiting an input device in response to it being placed in the off state, transmitting an inhibit message from the input device to the electrical control device, removing electrical power from the load in response to the inhibit message, inhibiting the electrical control device from responding to commands issued by any of the input devices to apply electrical power to the load until all input devices are removed from the off state, transmitting a feedback inhibit message from the electrical control device to each of the input devices and inhibiting all input devices from activating the electrical control device to apply electrical power to the load until all input devices are removed from the off state.
Further, there is provided in accordance with the present invention an apparatus for inhibiting the normal operating mode of a plurality of nodes logically connected to an electrical control device, comprising means for placing at least one of the nodes into the off state, means for communicating to the electrical control device the fact that the node has been placed in the off state and means for inhibiting the electrical control device, in response to the communication, from activating an electrical load connected thereto until each of the plurality of nodes is removed from the off state.